I addressed this question in an answer I wrote a few years back (this came up when Chernobyl came out, because they quote that piece at the end of the miniseries).

The short answer is no - the Chernobyl incident is not considered to have led to the dissolution of the USSR. The accident was a prompt for Gorbachev to intensify his reforms, notably those around trying to reduce Cold War tensions that could lead to a nuclear war, as I write here. But it was the forces of nationalism and republican control (as well as economic chaos) that Gorbachev released with his reforms that actually led to the dissolution of the USSR half a decade after Chernobyl.